Semiconductor device and method of manufacturing the same

Abstract

A semiconductor device according to an embodiment includes a first conductor, a first oxide semiconductor, a first insulator, a second conductor, a third conductor, and a fourth conductor. The first oxide semiconductor contacts, at one end, the first conductor, and extends in a first direction intersecting a surface of the first conductor. The first insulator surrounds a side surface of the first oxide semiconductor. The second conductor and the first oxide semiconductor interpose the first insulator therebetween. The third conductor contacts another end of the first oxide semiconductor. The fourth conductor extends in a second direction intersecting the first direction, and contacts a second conductor on a side opposite to the first insulator. The second conductor is of a material with a higher work function than a material of the fourth conductor.

What is claimed is: 
     
         1 . A semiconductor device, comprising:
 a first conductor;   a first oxide semiconductor contacting, at one end, the first conductor, and extending in a first direction intersecting a surface of the first conductor;   a first insulator surrounding a side surface of the first oxide semiconductor;   a second conductor, the second conductor and the first oxide semiconductor interposing the first insulator therebetween;   a third conductor contacting another end of the first oxide semiconductor; and   a fourth conductor extending in a second direction intersecting the first direction, and contacting the second conductor on a side opposite to the first insulator, wherein   the second conductor is of a material with a higher work function than a material of the fourth conductor.   
     
     
         2 . The semiconductor device according to  claim 1 , wherein
 the second conductor surrounds an entire outer periphery of the first insulator in a top view.   
     
     
         3 . The semiconductor device according to  claim 2 , wherein
 the second conductor surrounds the first insulator with a substantially uniform thickness.   
     
     
         4 . The semiconductor device according to  claim 1 , wherein
 the fourth conductor has an electrical conductivity higher than an electrical conductivity of the second conductor.   
     
     
         5 . The semiconductor device according to  claim 1 , wherein
 the second conductor contains one of Mo, Ni, Cu, Co, Se, TaC, Pd, Au, Ir, Pt, Re, RuO 2 , InSnO, SbSnO, WO, Rho, OsO, IrO, SrRuO, LaRhO, SrMoO, LaTiO, p-type Si, or p-type Ge.   
     
     
         6 . The semiconductor device according to  claim 1 , wherein
 the fourth conductor contains one of W, Cu, Mo, Ru, Rh, Co, AlCu, NiAl, or RuAl.   
     
     
         7 . The semiconductor device according to  claim 1 , wherein
 the second conductor has a work function higher than 4.8 eV.   
     
     
         8 . The semiconductor device according to  claim 1 , wherein
 the fourth conductor further includes a portion surrounding an entire outer periphery of the second conductor in a top view.   
     
     
         9 . A method of manufacturing a semiconductor device, comprising:
 sequentially forming, on a first conductor, a first insulator, a second conductor, and a second insulator;   forming a hole in which a top surface of the first conductor and side surfaces of the first insulator, the second conductor, and the second insulator are exposed;   etching a portion of the second conductor from the hole;   forming a third conductor in the etched portion of the second conductor;   burying a sacrificial member in the hole;   removing the second insulator and applying a protective member onto the second conductor;   etching a portion of the second conductor other than a region in which the protective member is applied and a region therebelow;   forming a third insulator on the second conductor; and   forming a pillar including an oxide semiconductor in a region from which the sacrificial member has been removed, wherein   the third conductor contacts a side surface of the pillar,   the second conductor extends in a first direction, and contacts, on a side opposite to the pillar, the third conductor, and   the third conductor is of a material with a higher work function than a material of the second conductor.   
     
     
         10 . The method of manufacturing the semiconductor device according to  claim 9 , wherein
 the third conductor surrounds an entire outer periphery of the pillar in a top view.   
     
     
         11 . The method of manufacturing the semiconductor device according to  claim 9 , wherein
 the third conductor contains one of Mo, Ni, Cu, Co, Se, TaC, Pd, Au, Ir, Pt, Re, RuO 2 , InSnO, SbSnO, WO, RhO, OsO, IrO, SrRuO, LaRhO, SrMoO, LaTiO, p-type Si, or p-type Ge.   
     
     
         12 . The method of manufacturing the semiconductor device according to  claim 9 , wherein
 the second conductor contains one of W, Cu, Mo, Ru, Rh, Co, AlCu, NiAl, or RuAl.   
     
     
         13 . A semiconductor device, comprising:
 a first conductor;   a first oxide semiconductor contacting, at one end, the first conductor, and extending in a first direction intersecting a surface of the first conductor;   a first insulator surrounding a side surface of the first oxide semiconductor;   a second conductor extending in a second direction intersecting the first direction, the second conductor and the first oxide semiconductor interposing the first insulator therebetween;   a second oxide semiconductor contacting another end of the first oxide semiconductor; and   a third conductor on the second oxide semiconductor, wherein   the second oxide semiconductor has a larger area than the first oxide semiconductor in a top view.   
     
     
         14 . The semiconductor device according to  claim 13 , wherein
 the second oxide semiconductor and the third conductor extend in a third direction intersecting the first direction and the second direction.   
     
     
         15 . The semiconductor device according to  claim 13 , wherein
 a Schottky barrier formed between the second oxide semiconductor and the first oxide semiconductor is smaller than a Schottky barrier formed between the second oxide semiconductor and the third conductor.   
     
     
         16 . The semiconductor device according to  claim 13 , wherein
 the first oxide semiconductor is of a material identical to a material of the second oxide semiconductor.   
     
     
         17 . The semiconductor device according to  claim 13 , wherein
 the first oxide semiconductor contains at least one of In, Zn, or Sn.   
     
     
         18 . The semiconductor device according to  claim 13 , further comprising:
 a fourth conductor between the second oxide semiconductor and the third conductor, wherein   the third conductor contains W, and   the fourth conductor contains one of indium tin oxide or an oxide semiconductor different from the first oxide semiconductor.   
     
     
         19 . The semiconductor device according to  claim 13 , wherein
 an upper portion of the first oxide semiconductor has a thickness larger than a thickness of a lower portion of the first oxide semiconductor, and   a side surface of the lower portion of the first oxide semiconductor is not positioned on an extension of a side surface of the upper portion of the first oxide semiconductor.   
     
     
         20 . The semiconductor device according to  claim 13 , wherein
 the second oxide semiconductor is provided on a bottom surface and a side surface of the third conductor.